The advantages have long been recognized in providing an apparatus for automatically and directly translating analog signals having characteristic frequencies and durations, e.g., musical tones or notes, into visible representations of the analog signals. Such a system has particular applicability in translating musical tones directly into visible representations of the notes played in the form of sheet music. The automatic transcription of the tones to sheet music frees the composer or performer of the tones from the constant need to interrupt playing in order to write down the notes. Such constant interruptions are disruptive of the composing process and cause inefficient use of the composer's time.
The prior art shows, for the most part, two ways for providing this automatic transcription. The first method requires the attachment of mechanical devices to the particular musical instrument being used to sense the movement of the keys of the musical instrument and to transmit them to a transcription device. This arrangement has the inherent disadvantages of requiring bulky mechanical couplings to the musical instrument and requiring that the composing process only occur when such mechanical couplings are available.
The second type of prior art device for automatic transcription requires a large array of band pass filters tuned to the array of frequencies to be transcribed. Such arrays are not only expensive but restrict the flexibility of the device to these selected frequencies.